E-mail has grown from a niche product to a primary means of communication in a relatively short period of time. Along with this massive rise in popularity, however, e-mail has also spawned a cottage industry of spamming, phishing, and other malicious or annoying communications. Spam is generally unsolicited commercial advertising. E-mail spam, also known as bulk or junk e-mail, is a subset of spam that involves sending nearly identical messages to numerous recipients by e-mail. In general, e-mail spamming is the abuse of electronic messaging systems to indiscriminately send unsolicited, unwanted or annoying bulk messages.
While spam generally wastes time and can be annoying, for the most part it does not cause direct financial harm to the recipient (although the resources that spam utilizes can indirectly cost money, such as, for example, bandwidth costs rising). There are other types of communications which are more malicious. These include communications with viruses or worms, as well as so called “phishing” attacks. A phishing attack is one where the sender is posing as a legitimate sender in order to entice the recipient to respond with personal information that could then be used to steal money. For example, a phishing attack may include a communication purportedly from a bank requesting that the recipient enter his bank account information in order to correct a problem or access a service. Upon transmission of the account information, the user's bank account is cleaned out by the malicious initiator of the attack.
There have been many attempts to filter e-mail messages in order to reduce or eliminate malicious or annoying messages, but none has been totally satisfactory. One method is to simply provide the user with the ability to mark certain senders as being on a “blocked” list. E-mail messages from senders on the “blocked” list then are blocked prior to being read by the user. This method can also be modified to search for certain terms or phrases in the subject or body of the email, and to block corresponding e-mail messages with matching terms or phrases. These methods suffer from the disadvantage, however, of requiring user interaction in order to set up and update the settings. Additionally, many savvy malicious senders have learned to modify the source addresses of their communications or to make minor modifications to the texts of the subjects or bodies of email so that each email is unique, making it difficult to block repeated e-mail messages.
Other approaches have involved setting up block lists more centrally, such as on an email server. Email is transmitted from one user to another through one or more email servers, which receive and direct the e-mail messages. While utilizing block lists on email servers shifts the burden of setting up and maintaining the lists to service providers or companies, these block lists can still be fooled by savvy senders.
Another approach is to verify the authenticity of an email using some sort of security system. Common such systems include certificates or key-based systems. This approach, however, requires that the sender of the email transmit a certificate with the email or utilize one or more security keys when generating or sending the email. This can be a complicated process and most individual users do not have the ability to perform such complicated email algorithms prior to sending an email. This approach also adds processing time to the processing of the e-mail messages, as the certificates or keys must be read and verified.
Considering these previous approaches and their disadvantages, an email filtering system is desired that would be more effective than prior art techniques.